Ramie fiber separation



Patented Aug. 24, 1954 OFFICE RAMIE FIBER. SEPARATION Jacobus Rinse,Bernardsville, N. J.

No Drawing. Application October 23, 1951, Serial No. 252,790

This invention relates to a process for the separation of the fibersfrom raw ramie fibrous masses without substantially impairingflexibility, strength and other desirable characteristics of theindividual fibers, thereby providing the fibers in a condition suitablefor the production of cloth and other articles of commerce.

Heretofore attempts have been made to separate the individual ramiefibers from raw ramie fibrous massees wherein the cellulosic fibers arebound together with natural binding substances, such as gums, lignins,and the like, by subjecting the fibrous masses to the action ofrelatively strong alkalies, such as sodium hydroxide, sodium silicates,trisodium phosphate, or the like. In such prior treatments, however, inorder to 3 Claims. (Cl. 92 l) from each other, and then, most desirablyfurther treating the fibers with a dilute acid solution to effect morecomplete separation of the fibers. The correlation of the conditionsemployed during the alkali-zinc oxide treatment of ramie may be andgenerally is different from that required in the treatment of agave andManila hemp fibrous masses. The treatment conditions of the ramieusually must be weaker.

In my preferred mode of operation the raw fibers (fibrous masses) aretreated in a hot alkali make such chemicals suficiently active to removeI the natural binding substances it has been necessary to use such hightemperatures or concentrations of alkalies, or both, that the tensilestrength of the fibers has been considerably reduced and an appreciableloss of cellulosic materials has occurred. 1

In copending application, Serial Number 46,372, filed on August 26,1948, by Hendricusstephanus and myself, now U. S. Patent No. 2,591,315,we have described a process for separating the fibers from raw agave orManila hemp fibrous masses Without substantially impairing the qualityof the recovered fibers. Broadly considered, the process involvescontacting the fibrous masses with an aqueous alkali metal hydroxidesolution of about 3-15% concentration (calculated as sodium hydroxide)containing dissolved therein at least 0.5% (calculated as oxide) ofeither aluminum or zinc oxides or hydroxides, or both, until the bindingsubstances are substantially dissolved, removing the solution containingthe binding substances dissolved therein from the freed fibers, thenwashing with water at ordinary, temperatures to remove the residualsolution, and finally drying. Now I have found that the fibers of rawramie can be recovered without substantially impairing the strength ofthe recovered cellulosio fibers'by subjecting the raw ramie to a hotaqueous solution of an alkali metal hydroxide of about 23-15%concentration (calculated as sodium hydroxide) containin dissolvedtherein at least 0.5% of zinc oxide or hydroxide whereby bindingsubstances are gelatinized but not removed,

next subjecting the fibers, which are still bound together, to theaction of hot-water at a temperature of at least 70 (3., whereby thefibers are substantially freed of binder and separated time of treatmentare metal hydroxide solution at concentrations below 15%, generally at3l.0% strength, at elevated temperatures of the order of -100 C.,preferably Bil-100 C.,' for a period of time of from to 2 hours.Superatmospheric pressures and temperatures over 100 C. can be usedprovided the strength of the alkaline solution and the regulated suchthat the fibers are not weakened to any substantial degree, butordinarily such conditions are not necessary or desirable.

The quantity of zinc oxide or hydroxide in the aqueous alkali solutionshould be at least 0.5% (calculated as oxide). The maximum quantityutilizable is usuallydetermined by the solubility of the zinc ion in thealkali metal hydroxide solution employed. From 1 to 6% of zinc oxide orhydroxide, (calculated as oxide) is preferably employed. f

The'concentration of the ingredients in the aqueous alkali metalhydroxide solution, the ternperatureand the time employed in my processare correlated in such manner that the binding or encrustatingsubstances between the fibers, such as pectins, lignins, gums, or othernatural binding substances, are softened and swollen and ,the gumstransformed into a gel while at the same time leaving the individualfibers substantially unattacked. The binding substances, therefore, arenot appreciably removed by this treatment and the fibers are'notseparated thereby. Solutions of alkalifmetal hydroxide other than sodiumhydroxide maybe used to like effect.

After ,thetreatment of the fibrous masses with the alkaline solutions ofalkali metal hydroxides and oxy-compoundsof'zinc, the resulting fibersare squeezed to remove excess solution and then continually(intermittently or continuously) subjected to the action of hot Water ata temperature of at least '70 ;C., and preferably at temperatures of-100 ;C L,; until the gelatinizednatural bind.- ing substances'a-resubstantially removed from between the cellulosic:fibers.' The-fibersmay require repeated or prolonged treatment with fresh hot water, thetreatment being continued until the used water is no longer discolored.Clear water indicates that most, if not all, of the gelatinized bindingsubstances have been dissolved out or removed.

After the treatment with hot water, a small amount of the bindingsubstance may remain, but the adhesion remaining between some of thefibers is greatly weakened. Any residual adhesion among the fibers canbe destroyed by subjecting the fibers to the action of a dilute organicor inorganic acid, such as hydrochloric acid or acetic acid. Theconcentration of the dilute acid is adjusted such that the strength ofthe acid is not suificient to injure the cellulosic fibers and such thatthe time of treatment is not uneconomically long. The subjecion of thefibers to the action of a to 1% hydrochloric acid solution or a l-5 orlesser concentrated solution of acetic acid or gluconic acid at fromroom temperature to about 60 C. for a period of from 5 to 60 minutesusually enough to free the fibers and leave them in a condition suitablefor the formation of fabrics and other articles of commerce.

After the acid treatment the fibers are washed and dried. Strong,flexible cellulosic fibers are thereby obtained.

After completion of the process, the fibers may be subjected tobleaching, softening, hackling, or other treatments customarily appliedto fibers before they are spun into yarns or woven into fabrics.

The following examples further illustrate the invention wherein theamounts of fibers and reagents employed are expressed in parts byweight.

One thousand grams of crude Florida ramie is heated for a period of 90minutes at 95 C. with an aqueous solution containing 6% sodium hydroxideand 1% zinc oxide. After removal of the solution, the fibrous mass inwhich the fibers are still bound together is treated several times withwater of 80 C. until the used water is no longer colored, at which timethe fibers will have been substantially separated. Thereafter the massistransferred to a water bath containing [2% of H01 maintained atapproximately room temperatures or from -30 C. The ramie remains in thisbath until the residual adhesion among the fibers is sufiicientlyweakened such that the fibers are well adapted to further conventionalprocessing. fter the fibers are subjected to the treatment in the .acidbath, they are washed with water and then dried.

Example 2 One thousand grams of crude or raw Japanese ramie is heatedfor a period of 60 minutes at 98 C. with an aqueous solution containing8% of sodium hydroxide and 1.3% of zinc oxide. The solution is thenremoved from the fibrous mass. After several treatments with water of 80C., the water is no longer colored and the gelatinized gums formed inthe alkali treatment and other natural binding substances aresubstantially removed. The fibers, substantially freed of the bindingsubstances are then transferred to an aqueous bath containing 1% aceticacid maintained at about 20-30 C. After treatment in the acetic acidbath and several washings with fresh water, the cellulosic fibers aresufiiciently separated or loosened to permit their further processingand use in accordance with known techniques.

Example 3 One thousand grams of raw Florida ramie is heated for a periodof 1 hour at C. in an aqueous soution containing 11.6% of sodiumhydroxide and 4.7% of zinc oxide. A white precipitate of zinc hydroxideforms and at the same time the natural gums binding the fibers togetherare gelatinized and rendered soluble. The treated fibers are thentreated several times with water at 90 C. until the water is no longercolored. The fibers with substantially all of the natural bindingsubstances removed are then transferred to an aqueous bath containing 1%gluconic acid vmaintained at 2030 C. and are retained in this bath untilthe fibers are sufficiently free to render them suitable for furtherconventional processing. Upon removal from the gluconic acid bath thefibers are repeatedly washed with pure water and upon drying the fibersare ready for the processing.

The process of the present invention has the outstanding advantage thatthe treatment conditions may readily be so chosen that the undesiredbinding components of the raw fibrous masses, such as pectin, lignin,gums, and the like, can be dissolved out without the cellulosic fibersthemselves being chemically attacked to any substantial degree. As aresult, substances cross-linking or binding the fibers together areremoved and the fibers retain substantially their original length andtensile strength. The process also has the additional advantage that theloss of cellulosic material is ordinarily very small. he process has theadditional advantage that it is not necessary to pro-bleach the fibers,hence the costs and the detrimental effects of such preibleachingoperations are avoided.

The practice of this invention has been exemplified herein by variousdetailed conditions and examples which are included for illustrativepurposes. It wi l be understood, therefore, that these conditions may bevaried somewhat without departing from the spirit or the scope of theinvention defined by the appended claims.

What is claimed is:

l. A process for the production of flexible, cellulosic fibers from rawramie fibrous masses, the individual fibers of which are bound togetherwith lignin and other natural binding substances, which comprisescontacting the said fibrous masses at a temperature between about 80-100C. with an aqueous alkali metal hydroxide solution of between about 340%concentration (calculated as sodium hydroxide) containing dissolvedtherein from 145% (calcu-- lated as oxide) of a compound selected fromzinc oxide and zinc hydroxide for a period of onehalf to two hours untilnatural binding substances are gelatiniaed while leaving the cellu--losic fibers substantially free from attack, subjecting the fiberscontinually to the action of hot water at temperatures of from IO- C.until the used water is no longer substantially discolored by matterremoved from the fibers, and subjecting the fibers to a treatment in adilute acid solution to free remaining adhering fibers, whereby strong,flexible, cellulosic fibers are obtained.

2. A process for the production of flexible, cellulosic fibers from rawramie fibrous masses, the individual fibers of which are bound togetherwith lignin and other natural binding substances, which comprisescontacting the said fibrous masses at a temperature between about80-100" C. with an aqueous sodium hydroxide solution of between about340% concentration containing dissolved therein from 1-6% (calculated asoxide) of a compound selected from zinc oxide and zinc hydroxide for aperiod of one-half to two hours until natural binding substances aregelatinized while leaving the cellulosic fibers substantially free fromattack, subjecting the fibers continuously to the action of hot water attemperatures of from 80-100 C. until the used water is no longersubstantially discolored by matter removed from the fibers, subjectingthe fibers to a treatment in a dilute acid solution to free remainingadhering fibers, rinsing with water and drying the fibers, wherebystrong, fiexible, cellulosic fibers are obtained.

3. A process for the production of flexible, cellulosic fibers from rawramie fibrous masses, the individual fibers of which are bound togetherwith lignin and other natural binding substances, which comprisescontacting the said fibrous masses at temperatures between 80-100 C.with an aqueous sodium hydroxide solution of between 23-10%concentration (calculated as sodium hydroxide) containing dissolvedtherein at least 0.5% (calculated as oxide) of a compound selected fromzinc oxide and zinc hydroxide for a period of to 2 hours whereupon the"binding substances will be transformed into a gelatinized mass whichcan be removed by the action of hot water while leaving the cellulosicfibers substantilaly free from attack, continually subjecting thefibrous masses to the action of hot water at a temperature of from'70-100 C. until the binding substances are substantially removed,subjecting the fibers obtained to the action of a dilute acid solutionat substantially room temperatures to free remaining adhering fibers,whereby strong, flexible, cellulosic fibers are obtained.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 55,386 Dixon June 26, 1866 1,630,365 Weber May 31, 19272,527,141 Mantell Oct. 24, 1950 2,530,244 Jensen Nov. 14, 1950 2,536,334Weiss Jan. 2, 1951 2,591,315 Stephanus et a1 Apr. 1, 1952 FOREIGNPATENTS Number Country Date 20,314 Great Britain Dec. 17, 1890 of 1889324,520 Germany Aug. 28, 1920

1. A PROCESS FOR THE PRODUCTION OF FLEXIBLE, CELLULOSIC FIBERS FROM RAWRAMIE FIBROUS MASSES, THE INDIVIDUAL FIBERS OF WHICH ARE BOUND TOGETHERWITH LIGNIN AND OTHER NATURAL BINDING SUBSTANCES, WHICH COMPRISESCONTACTING THE SAID FIBROUS MASSES AT A TEMPERATURE BETWEEN ABOUT80-100* C. WITH AN AQUEOUS ALKALI METAL HYDROXIDE SOLUTION OF BETWEENABOUT 3-10% CONCENTRATION (CALCULATED AS SODIUM HYDROXIDE) CONTAININGDISSOLVED THEREIN FROM 1-6% (CALCULATED AS OXIDE) OF A COMPOUND SELECTEDFROM ZINC OXIDE AND ZINC HYDROXIDE FOR A PERIOD OF ONEHALF TO TWO HOURSUNTIL NATURAL BINDING SUBSTANCES ARE GELATINIZED WHILE LEAVING THECELLULOSIC FIBERS SUBSTANTIALLY FREE FROM ATTACK, SUBJECTING THE FIBERSCONTINUALLY TO THE ACTION OF HOT WATER AT TEMPERATURE OF FROM 70-100* C.UNTIL THE USED WATER IS NO LONGER SUBSTANTIALLY DISCOLORED BY MATTERREMOVED FROM THE FIBERS, AND SUBJECTING THE FIBERS TO A TREATMENT IN ADILUTE ACID SOLUTION TO FREE REMAINING ADHERING FIBERS, WHEREBY STRONG,FLEXIBLE, CELLULOSIC FIBERS ARE OBTAINED.